There is proposed an engine start control system that allows an engine start in accordance with a collation result of a master ID code stored in a vehicle and a slave ID code stored in a vehicle key fob or in a key transponder (refer to JP-08-133016-A, for example). The engine start control system is generally designated as an immobilizer system.
When the engine start control system does not authorize the slave ID code, the system executes a starter locking procedure, that is, sets an engine control unit in a starter locked state to prevent unauthorized person from starting an engine. An immobilizer control unit, which is separated from the engine control unit, performs the engine start lock procedure. The engine control unit performs an engine start control in accordance with an immobilizer set state signal or an immobilizer released state signal transmitted from the immobilizer control unit. When the engine start control system authorizes the slave ID code, the system executes a starter unlocking procedure, that is, sets an engine control unit in a starter unlocked state to allow a driver to start the engine.
Most immobilizer systems in actual use include steering lock and unlock procedures to lock and unlock a steering lock to improve a security. In the immobilizer system with the steering lock and unlock procedures, it is necessary to prevent the engine from starting before the steering lock is unlocked. Thus, when the system authorizes the slave ID code, the system unlocks the steering lock, and then releases the immobilizer system to allow the engine start.
In a conventional engine start control system, a starter switch of an engine is operated by turning a key inserted in a key cylinder located at a side of a steering shaft. Most recent vehicles are provided with the steering lock installed in the key cylinder. The steering lock is released in a rotational stroke of the starter switch from a lock position (OFF position) to an engine starting position. Conventional immobilizer systems are developed based on this engine start control system. That is, a transponder installed in a key fob memorizes the slave ID code, and a radio frequency (RF) circuit installed in the key cylinder reads the slave ID code. When the slave ID code is authorized, the immobilizer system allows a turn operation of the key inserted in the key cylinder to unlock the steering lock and then to start the engine. From a viewpoint of an internal processing by a computer in the immobilizer system, the immobilizer is released on a condition that the steeling lock is unlocked, and then the engine is started by turning the key up to the engine starting position. An operation of the engine start control system having the above-mentioned structure of the immobilizer is as same as that of a normal engine start control system having no immobilizer system to a driver's operation, except for a case that the slave ID code is not authorized. Thus, the driver can start the engine without feeling odd in the operation. This feature is derived from a manually operable mechanism of the steering lock associated with a turn operation of the starter switch.
Current vehicles have engine start control systems with no manual key operation. For instance, in the engine start control system generally designated as a smart key and push button start system, a wireless communication between a key transponder carried by the driver and a transmission and reception unit mounted on the vehicle proceeds with an unlocking procedure of a door lock, an authorization procedure of the slave ID code, and so on. Specifically, when the driver rides on the vehicle and steps on a brake pedal or a clutch pedal, the engine is started by pressing an engine starting switch while the brake pedal (in a vehicle with automatic transmission) or the clutch pedal (in a vehicle with a manual transmission) is stepped on. In this engine start control system, no manual key operation is associated with the engine starting procedure. Thus, the steering lock is also computerized and operated automatically in control procedures of the immobilizer system.
As a result, the procedure to release the immobilizer system is as follows. When the driver steps on the brake pedal, a wireless communication between the key transponder and the immobilizer system executes an authorization process of the slave ID code stored in the key transponder. Then, in a state that the slave ID code is authorized, when the driver presses the engine starting switch, the immobilizer system unlocks the steering lock, releases the immobilizer system, and then starts the engine. In this engine start control system, however, the steering unlock procedure with mechanical motion is processed between the driver's operation of the engine starting switch and an actual engine start, so that the driver feels odd because the engine does not start rapidly, that is, because of a relatively long delay from the engine starting operation to the actual engine start.